1. Field of the Invention
The present invention relates to a flexible backrest, in particular but not exclusively a wheelchair backrest, having a contour that can be easily adjusted to the morphology and anthropometry of a user's back.
2. Brief Description of the Prior Art
Manual wheelchairs usually come with conventional sling backrests. Originally, this type of backrest was designed to enable easy folding of the wheelchair. However, some studies have demonstrated that prolonged use thereof may negatively affect user's posture, comfort, function and health (Zollars, J. & Axelson, P. (1993) "The back support shaping system: an alternative for persons using wheelchairs with sling upholstery", Proceedings of the 16.sup.th Annual RESNA Conference, Las Vegas, RESNA Press, 274-276; Harms, M. (1990) "Effects of wheelchair design on posture and comfort of users", Physiotherapy, 76, 5, 266-271; Bergen, A. & Presperin, J. (1990), "Positioning for functions: wheelchairs and other assistive technologies", Valhalla Rehabilitation Publications Ltd; and Zacharkow, D. (1984), "Wheelchair posture and pressure sores", Springfield, Ill.). In fact, they may cause the spine to curve into a kyphotic geometry and produce a posterior tilting of the pelvis, which can lead to back and neck pain, and even to long-term deformities of the spine and pelvis. Moreover, conventional sling backrests do not provide sufficient lateral trunk support to prevent, manage or correct trunk alignment problems.
Considering these problems, the development of special seating for people with disabilities become important. The technology in seating has rapidly evolved around cushions or combination of rigid interfaces and cushions with great results. There is a general consensus that, from a posture standpoint, they offer some of the best solutions (Valiquette, C. & Audet, J. (1992) "Pushing the limits of the sling concept: the contoured sling backrest" Canadian seating and mobility conference, Toronto). Unfortunately, the use of cushions deprives many wheelchair users of the advantages of the sling backrests such as foldability, light weight, low cost and simplicity (Valiquette, C. & Audet J. (1992), "Pushing the limits of the sling concept: the contoured sling backrest", Canadian seating and mobility conference, Toronto; and Zollars J. & Axelson P. (1993), "The back support shaping system: an alternative for person using wheelchairs with sling upholstery", Proceedings of the 16.sup.th Annual RESNA Conference, Las Vegas: RESNA Press, 274-276).
In this way, adjustable-tension back upholstery was introduced on the market to preserve the sling backrests characteristics while improving the user's posture and comfort. Adjustable-tension back upholstery are foldable and can accommodate lumbar lordosis or kyphosis by the use of adjustable straps. In spite of the improvement, they often give poor lateral trunk support and some adjustments are still missing to maintain neutral pelvic position and lumbar lordosis. Given this context, the conception of a new backrest for wheelchair is worthwhile.